There are a variety of ways to artificially lift liquids from oil and gas wells. One of these is called a plunger or plunger lift which is commonly used to lift water, hydrocarbon liquid or a combination thereof from a gas well. The original plunger was a one piece piston. The well was shut in and the piston dropped into the well. When it reached the bottom, the well was opened so gas below the piston would push the piston and any liquid above it to the surface. More modern plungers are two piece affairs, i.e. a sleeve and a ball as shown in U.S. Pat. Nos. 6,467,541 and 6,719,060, the disclosures of which are incorporated herein by reference. When the sleeve and ball reach the surface, the sleeve passes onto a rod which dislodges the ball causing it to fall back into the well. The sleeve is held for a while at the surface and is usually dropped in response to a command from a controller. When the sleeve falls and reaches the bottom of the well, it meets up with the ball so gas from below pushes the sleeve and ball to the surface thereby removing some liquid from the well. The removal of liquid allows more gas to be produced from the well.
Two piece plunger lifts have been successful in prolonging the life of gas wells because they remove liquid during each cycle and do not require the well to be shut in. A problem with any artificial lift system is that wells do not act consistently, i.e. they produce only gas for a while, produce a lot of liquid for a while, produce both gas and liquid at varying rates, sometimes produce nothing at all and otherwise defy operation by a computer or controller.
Disclosures of some interest are found in U.S. Pat. Nos. 4,070,134; 4,712,981; 4,986,727; 6,637,510; 6,851,450; 7,021,387; 7,121,335; 7,134,503; 7,438,125; 7,784,549; Canada 2,504,503 and Russia 1,756,628.